Gene therapy has emerged as a new approach treating genetic disorders by delivering therapeutic genes to targeted diseased tissues, and has been proven to be an effective approach for cancer treatments with few side effects. The currently used gene vectors can be divided into viral vectors and non-viral vectors. Non-viral gene vectors including cationic lipids, polymers, dendrimers and peptides are particularly attractive in terms of safety, low immunogenicity, biocompatibility, and the potential for large-scale manufacture. However, their applications are bottlenecked by low transfection efficiency compared with viral vectors.
In nonviral gene delivery, cationic polymers are generally used to neutralize the negative charges of DNA and condense the large macromolecules into nanoparticles to protect them from DNA degradation and facilitate its cellular internalization. However, DNA/polymer complexes (polyplexes) are thermodynamically stable and inherently resistant to dissociation, which is necessary to release the DNA for transcription once inside the cell. Therefore, smart designs are required to facilitate DNA release by exploiting intracellular microenvironment, thus increasing the efficacy of nucleotide drugs. The present invention provides preparation methods of such polymers, which can condense DNA into polyplexes but, once inside cell, lose their positive charges to quickly release the packed DNA, thus facilitating DNA expression.
Due to the abnormal physiological characteristics of tumor, tumor tissues will generate a large amount of reactive oxygen species (ROS), including hydrogen peroxide (H2O2), superoxide anion (O2.), hydroxyl radicals (OH.), which can oxidize phenylboronate acid/esters into phenolic groups, thus activating the p-hydroxylmethylphenol-shedding reaction (Broaders, K. E.; Grandhe, S.; Frechet, J. M., A biocompatible oxidation-triggered carrier polymer with potential in therapeutics. J Am Chem Soc 2011, 133 (4), 756-8.). Boronate acid could form cyclic esters with diols, thus enhancing its interaction with cancerous cells or nucleotide of DNA or RNA in gene delivery. (Piest, M.; Engbersen, J. F., Role of boronic acid moieties in poly(amido amine)s for gene delivery. J Control Release 2011, 155 (2), 331-40.). Moreover, boronate acid/esters is not toxic towards human body.
The present invention presents the preparation of p-benylboronate acid/esters substituted quaternary ammonium-containing polymers, which have the ability to undergo positive to negative charge-reversal upon oxidation of the benzylboronate acid/esters group by intracellular ROS and demonstrates that such polymers are more efficiently deliver DNA and induce gene expression. There is no report on such polymer, nor its preparation method or application.